Getsu Fuma Den
Konami really enjoyed making weird games back in the NES era. They rarely found a title they couldn't add in some elements of the Metroidvania genre (even before that genre had a name). If they had a platformer you could expect them to shove in some item collection, a explorable overworld, and more. They wanted you to really explore their games and not just sit down for a quick 15 minute section.
The Japan-exclusive Getsu Fuma Den neatly fits into that development style. Released in 1987, the game features a strange blend of overworld exploration, linear combat zones, and over-the-shoulder dungeon crawling, all to aid in the quest of demon hunter Getsu Fuma. It is, frankly, a real oddity (and I say that having played through Konami Wai Wai World.
That's likely the reason this title didn't get a release outside Japan. It's weirdness, along with it's demon-based mythology and religious themes (which Nintendo of America usually had edited out of games for the West) made this title a hard sell for Western audiences (and porting it out of Japan). The game never even saw a sequel, despite it having a number of charms. While the character of Getsu Fuma has lived on in other Konami titles, appearing in the Wai Wai World games, along with cameoing in other Konami releases, this game remains a weird one-of from a bygone era, a testament to the strangeness of many of Konami's ideas.